MTS试验机岩石压缩试验变形测量数据的选取方法研究

变形测量数据的选取对认识岩石力学性质及变形参数的计算有着重要影响.MTS试验机已被广泛应用于岩石力学试验中,其中岩石的变形测量常用方式有引伸计、LVDT和压板位移,这3种测量方法得到的轴向应变的准确性和适用性有待深入研究.本研究采用MTS试验机进行岩石的单轴和三轴压缩试验,对比引伸计、压板位移和LVDT 3种方式测量得...

SELECTION OF DEFORMATION MEASUREMENT DATA OF ROCK UNDER MTS COMPRESSION TESTS

This paper investigates the accuracy and applicability of axial strain obtained by axial extensometer, LVDT and press-plate displacement. We carried out the uniaxial and triaxial compression tests of rock with MTS testing machine, and compared the stress-strain curves obtained with the axial extensometer, press-plate displacement and LVDT. Furthermore, we analyzed the effects of the results under three different measurement methods on the shape, strength and deformation parameters of the stress-strain curves of rock samples. The results show that in the pre-peak strength stage, the deformation data measured by the plate displacement and LVDT, the stress threshold value and deformation parameters have large differences. So axial strain should adopt the axial extensometer to obtain the deformation data. In addition, when the deformation data measured by the axial extensometer reaches the peak strength, the axial strain can decrease, and this curve can be easily mistaken as a class Ⅱ curve. It is recommended to install a LVDT sensor at the fixed head of the MTS testing machine, and calculate the axial strain after peak strength with the axial deformation measured by LVDT. When the LVDT sensor is not allowed to be installed, we should adopt the pressure plate displacement measurement to represent the deformation of the sample after the peak strength.